Various types of ultrasonic scanners for cardiac studies are well known. Such scanning probes are disclosed, by way of example, in U.S. Pat. Nos. 4,543,960 and 4,841,979, and in published European patent application No. 039.045.
U.S. Pat. No. 4,543,960 discloses an ultrasonic transesophageal echo cardiography probe including a transducer array consisting of a number of transducer elements and rotatable about an axis having an orientation normal to the general plane of the transducer array. The mechanical rotation of the array in this arrangement is performed manually for the purpose of selecting desired scan or sector planes. Thus, no combination of motor-driven mechanical and electronic scanning is contemplated. The devices of U.S. Pat. No. 4,841,979 and published European patent application No. 039.045, on the other hand, employ a simple transducer and no transducer array. Both of these publications describe a rotary movement of the transducer, as well as the possibility of additional movement components, so as to cover a region in space.
A probe for image scanning into orthogonal sector planes from the esophagus has also been proposed. The probe uses two separate phased array transducers for obtaining such scanning. This solution, however, has obvious drawbacks in that each of the two transducer arrays must be independently connected by a large number of independent electrical leads. Moreover, the two arrays must of necessity be located in physcially different positions, resulting in different centers of the two orthogonal scan sectors. Thus, a direct comparative reference between the images and the Doppler velocity measurements from the two scan planes is difficult to obtain. The use of two independent transducer arrays also substantially increases the size of the probe, a highly undesirable and often unacceptable condition for carrying out cardiac imaging from the esophagus.